Wanderlust Nursery has Chilean Guava seeds listed but they're currently out of stock.
One Green World lists named varieties, but no seeds.
Pitangatuba is common among collectors here. Someone should be able to help you with this one.
Achacha is uncommon. A local specialty fruit market in Houston, TX - Linda's Tropical Fruits - got a limited quantity shipment of the fruit (six bags of 2lbs or so) during the summer of 2019. I was lucky to get a hold of a bag, but regret not saving the seeds. No telling if they were viable or not. I know of someone else who found an international market carrying them in New England, but do not know the details. So know they make it stateside once in a blue moon if you can't get a hold of seeds or seedling from a collector.
Olosapo is rare to show up in trades. I'd like a seedling myself.